Improved thermoelectric properties of Sb-doped Ti_0.5Zr_0.5NiSn alloy with refined structure induced by rapid synthesis processes

Thanks to the great advantage of preparation methods, the thermoelectric (TE) alloy materials can be fast synthesized with controllable structural morphology for optimizing charge and phonon transport properties, thereby improving the TE efficiency of the material. Herein, a series of Sb-doped Ti0.5Zr0.5NiSn1-xSbx based half-Heusler alloy was prepared via a combined fast procedure of arc melting (AC), melt spinning (MS) followed by spark plasma sintering (SPS). The detailed analyses of morphology, phase structure, and composition reveal high-quality samples through processes for enhanced TE properties. High ZT values over one are achieved for all samples with slight Sb doping content variation from x = 0.0025-0.02. The enhanced TE performance of the Sb-doped Ti0.5Zr0.5NiSn1-xSbx alloys here results from the synergistic between the approaches such as doping, alloying, nanostructuring, and the presence of nano-precipitates induced by MS. The highest ZT values of similar to 1.2 at 847 K with an average ZT of 0.798 and estimated TE conversion efficiency reached 12.8% in the temperature range from 300 K to 847 K were achieved for the 1.25% Sb doped sample. In addition, the thermal cycling test through continuous measurement of five and a half cycles confirmed the high thermal stability of the bulk alloy. High ZT and thermal stability based on Hf-free Ti0.5Zr0.5NiSn1-xSbx alloy and fast synthesis are well matched for commercial requirements.